Rapid truncation of star formation activities in massive galaxies across cosmic time

Po-Feng Wu^1*

¹Graduate Institute for Astrophysics, National Taiwan University, Taipei City, Taiwan

* Presenter:Po-Feng Wu, email:Wupofeng@phys.ntu.edu.tw

The succession of star formation in galaxies is one of the central and fundamental unsolved questions in galaxy evolution. Recent confirmation of massive galaxies with low star formation rate emerging within the first billion years of the universe puts galaxy formation theory to the test. There must be a highly efficient process to shut down star formation in galaxies at the cosmic dawn. Galaxies with recent truncation of star formation activities provide the best proxies to look into the process. From deep optical spectra of these galaxies, we can derive information about the past star formation activities, stellar kinematics, gas kinematics, and AGN in this key phase. All information puts important constraints on the physical mechanisms that drive the evolution of galaxies.

I will demonstrate that a period of centrally concentrated star formation preceded the truncation of star formation activities. AGN is elevated during this period. Gas outflow is more prevalent near the peak of the star formation, which can help clear out the gas reservoir and suppress the star formation. These circumstantial evidences combined suggest that a highly dissipative event that funnels gas into the center of galaxies is likely necessary at all cosmic epochs. In the coming years, the ongoing Prime Focus Spectrograph Subaru Strategic Program will obtain an unprecedented number of high-quality spectra of galaxies beyond z=1. Combining with the increasing coverage of images by the James Webb Space Telescope, we will sketch out the detailed process of the truncation of star formation in the first half of the universe. The IR capability of the JWST spectrographs will even push it to the first billion years of the universe, the epoch in which the first massive quiescent galaxy forms.

Keywords: galaxy evolution, quiescent galaxies, star formation quenching